The present invention relates to the pumping of corrosive liquids like sulfuric, nitric, perchloric, phosphoric, hydrofluoric, hydrobromic and other acids, bases, liquid halogens, etchants, etc. which are used in chemical and related industries.
It has been especially difficult to pump these liquids reliably at elevated temperatures like 150.degree. to 200.degree. C., as required in some chemical operations. In addition, corrosives may have to be pumped to higher pressure levels e.g., for loading or filtration purposes. Since electric motors have reliability problems in a corrosive environment, a pump of this type is usually driven by compressed air or nitrogen. Another consideration is avoidance of the use of metal in the liquid path, like for valve springs, since it severely limits the reliability of the pump.
Teflon is a plastic that can withstand chemical attack to a much better degree than most other materials. Teflon diaphragm pumps are successfully used but usually show diaphragm fatigue after some operating time at elevated temperatures. Other problems with Teflon are dimensional changes as a function of temperature which can result in leakage of liquid or working gas from the joints of assembled parts.
A new pump incorporating novel design features towards the solution of the problems mentioned above is detailed in the following description.